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spudgun range, are we falling short?

A place to ask general spud cannon related questions.
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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 9:32 am

I draw a quick sketch based on the Tall Boy drawing.

Here's what I could do with the materials I have at hand.
The 4 holes at an angle near the nose are exhausts to whatever is inside.

Materials are brass and aluminium.
The picture is scaled to 10 pixels = 1 mm

What do you think?
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Unread postAuthor: ramses » Sun Apr 03, 2011 12:39 pm

Since you are considering smoke powder, why not try flare composition? that would get you to a really bright beacon of light to replace the LED. Of course, it might require a night shot, but flares are quite visible during the day. If you drilled the back of the dart out to make room, this (and your smoke idea) would move COM forward, as well as provide a base bleed type effect to fill the wake.

Tech's idea about multiple spotters is good, so long as you don't somehow manage to hit one of them.
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Unread postAuthor: Ragnarok » Sun Apr 03, 2011 1:58 pm

Line of sight techniques like flares, LEDs, etc... they won't work.

If you've got a projectile that's been going fast and aerodynamic enough to travel kilometres, it will just hit the ground and go straight down through it. You'll be digging it out again.

If you're going to find it, you need something not reliant on line of sight. Smoke composition might work (as it would rise back up out of the hole made), but a flare wouldn't.

Personally, I'm surprised it's not possible to make a cheap radio transmitter and a receiver to track it.
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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 3:05 pm

Ragnarok wrote:Personally, I'm surprised it's not possible to make a cheap radio transmitter and a receiver to track it.


I'm sure it is, JSR shared some interesting links. But my electronics is so long ago that I have nothing remotely interesting to say about it :D
It will go forward and make this MiniBoy Mark I, with simply some holes in it, just in case it is useful. Let's keep the homing device for Mark II! ;)

Now I'm just wondering if the Brass + Aluminum have a chance to survive buried in the sand. My guess is that the shell will weight around 150 gr (empty). Can anyone with a similar experience can share it? I'm not talking about a direct hit on some hard object, just falling down in the sand.

Time to thing also about the sabot. I would like to make something so MrCrowley can reuse it, maybe with something else than my MiniBoy just in case it is lost at sea... :roll: So with some kind of diameter adjustment capabilities. Ideas? Which material have the best chance to survive? Aluminium? With a brass back maybe? Any change the flying parts could be kept somehow close together? (steel cable come to mind)
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Unread postAuthor: JDP12 » Sun Apr 03, 2011 3:21 pm

aluminum sabot will be heavy....

Look into some sort of dense foam with a solid backing. The stuff that electronics are sometimes packed into comes to mind. Not the gay stuff that sticks to everything, the other stuff,, don't know the name.

See JSR's mini hybrid thread. you can use foam, as long as it has a backing I think, that way it won't explode or deform.

As for connecting them, yea i'm sure you can, you'll just have to be careful that the cable won't interfere with the projectile. I don't really think you'll have to connect them, as the sabot separates almost instantly upon coming out of the barrel, so it will be very close to you.
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Unread postAuthor: MrCrowley » Sun Apr 03, 2011 3:56 pm

I did some more thinking about smoke and I'm wondering whether it could actually burn during flight or if there wont be enough oxygen, especially if the cavity is as large as the diagram above. Say the first quarter of the cavity is filled with steel wool, after that burns I'm not sure whether oxygen would still be able to reach the smoke powder.

Though, we still need a way to ignite the steel wool since the diagram above wont allow it to be ignited inside the barrel.
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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 6:04 pm

Here's my last thinking.

The tail now have 8 holes. When the sabot is in place, 4 are used as anchor points. So 4 are open to ignition gas.

The sabot is very light, made of 4 pieces of UHMW in front and in the back, linked with 4 brass rod. Will this have a chance to resist to the pressure and Gs?? I have no idea please tell me. Of course I could use steel threaded rods instead of brass.

The 2x 4 pieces of UHMW seem complicated to do but not really. The 4 pieces a gripped together in the lathe stock, then turned to size. A bit tricky, and I think fun to do too (well, fun when you like lathes).

Note that this is a sabot VERY specific to this particular shape :lol: Any other ideas? More generic maybe?

[edit] oh I forgot. In flight the whole 8 holes are open, and could supply the oxygen needed as well as exhausting fume. Would this be enough?
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Unread postAuthor: ramses » Sun Apr 03, 2011 7:22 pm

hmmm. I'm starting to think a radio beacon will be the best route. But as someone said a few pages back, it would be best if the destruction of the dart was required for recovery, rather than survival.

Barring that, a fuse the protrudes through the sabot would ignite, burn, and delay the smoke some , perhaps long enough to make the smoke comp burn only after the projectile had buried itself in the ground.That leaves the task of finding the hole in a wide area. Perhaps some sort of bright ribbon could be deployed vigorously after the smoke comp burns.
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Unread postAuthor: ilovefire » Sun Apr 03, 2011 7:26 pm

what about some sort of dye? like if you had a compartment full of red dye that breaks once it hits the sand then you would have a nice visual red patch? not sure how you would do it but just an idea
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why make it if it dosent shoot?
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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 7:48 pm

In the last design, a fuse can protrude from one of the holes, as they are outside the sabot.

I thought of dye... but it would be messy (this sand beach is so lovely ;-) ). Best would be a miniature QDV that exhaust from the holes after hitting a nose contact... like that Brocock cartridge but reversed (bottom first)...

But I think Ragnarok is right, the impact will bury it deep, and even more because it is sand. So I'm not sure if it would work. And that's quite complicated to build for a discardable shell... for Mark III maybe ;-)

I think all we can hope if nothing else work is a nice and large crater :lol:
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Unread postAuthor: ramses » Sun Apr 03, 2011 8:02 pm

Perhaps you could locate a used radio animal tracking device. The tags must be small, durable, and waterproof.
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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 8:05 pm

I'm afraid the receptor cost for such professional devices would be out of my league :lol: Maybe a student... ;-)
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Unread postAuthor: MrCrowley » Sun Apr 03, 2011 8:05 pm

That design looks pretty good. I think it will give the best chance for success if I used smoke powder so we may as well try it. I too have my doubts about smoke but all the other ideas seem a bit complicated except for maybe dye (which could be made to be nontoxic). A radiotransmitter would be pretty cool but I'm not sure how cheap I could make one for and whether it would survive the launch and landing.

Hahaha I just realised for the last 3 or 4 pages we've been breaking th rules regarding smoke powder. No one tell PCGUY, okay? :D

I think if I did the testing at low tide, I would have a much, much greater chance of finding the projectile assuming two things:
a) the projectile lands on wet sand
and
b) the tide doesn't come in fast enough to cover the landing zone.


edit: I would also be a little worried the 'pins' for the sabot will get stuck in the projectile during flight. If you prefer, LeMaudit, you can go with your original sabot as described in your PM where the rear of the projectile is sealed off but makes for a much more simple and basic sabot. I could then try and modify it to allow combustion gases to ignite the steel wool or I could just scrap the smoke idea and do as Tech said and have a few spotters up the beach.

You may still have to make the projectile hollow though, judging by jackssmirkingrevenge's calculations, ideal weight is somewhere around 100g even for such a small projectile.
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Unread postAuthor: LeMaudit » Sun Apr 03, 2011 8:16 pm

damnit... :oops:

nah nah... I was talking about smoke.. as in cigarettes.... bad english, french and all y'a know... didn't you see the center hole just fit one cigarette? With a nasty tobacco smell you should be able to find the thing... maybe with a dog's help...

With your experience with such powerful launcher, do you think the sabot would survive? or at least not crush inside the barrel? I really have no idea... no feeling at all if it's okay... I will surely replace the brass rods by stainless rods, just to be extra safe, but it's up to you and more experienced spuders to tell if it is safe for you to use that sabot design.
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Unread postAuthor: MrCrowley » Sun Apr 03, 2011 8:20 pm

The only problem would be the temperature in the barrel, as UHMW melts around 150 degrees celcius or so. I still think it could work, perhaps only once though.

I'm at Uni at the moment and need to study for a mid-semester but I'll get back to you in a couple of hours about more ideas for the sabot.
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